An ultrasonic transducer is assembled in an ultrasonic probe of an ultrasonic image pickup device to transmit/receive ultrasonic waves, and used in various usages such as diagnosis of tumors in human bodies and inspection of cracks generated in buildings.
The ultrasonic transducer equipped with a piezoelectric material has been used so far. In recent years, with the progress of MEMS technologies, a capacitive micromachined ultrasonic transducer (CMUT) is being actively developed for the commercialization in which a vibration portion is formed on a silicon substrate. The CMUT has advantages of a wide frequency range of available ultrasonic waves and of high sensitivity compared to the ultrasonic transducer equipped with the conventional piezoelectric material. In addition, since a technique of processing an LSI is used in the manufacturing, it is possible to perform micromachining, and it is suitable for Manufacturing a vibrator for the ultrasonic probe.
As a related art, for example, PTLs 1 to 3 disclose a single CMUT element and a CMUT which is disposed in an array.